1. Field of the Invention
The present invention relates generally to an optical fiber block for connecting a Planar Lightwave Circuit (PLC) to an optical fiber and, in particular, to an optical fiber block for coupling a ribbon fiber.
2. Description of the Related Art
A PLC is an optical device in the form of a chip, which is widely used for division, modulation, switching, and multiplexing of optical signals. To connect a pLC to an optical fiber in alignment, an optical block is typically used. The optical fiber block is made of silicon materials and fabricated by wet-etching techniques.
FIG. 1 illustrates a conventional PLC 10 used to connect the input of an optical block 12 and the output of optical fiber blocks 14. As shown in FIG. 1, the optical fiber blocks 12 and 14 connect the PLC 10 to a single fiber F1 and a ribbon fiber F2, respectively. A plurality of N wavelengths are inputted to the input port of the pLC 10 via the single fiber F1, then outputted to the ribbon fiber F2 through the pLC 10. The optical fiber blocks 12 and 14 are provided to fix the fibers F1 and F2 in alignment using an adhesive B, such as epoxy resin. Glass covers G1 and G2 are glued to the input and output sides of the PLC 10, and glass covers G3 and G4 are glued to hold the optical fiber blocks 12 and 14.
The alignment of the ribbon fiber F2 using the optical fiber block 14 and the glass cover G4 is further illustrated in FIG. 2. After the optical fiber block 14 is combined with the glass cover G4, both are polished at a predetermined angle θ with respect to a vertical line L1. The resulting polished surface 16 acts to reduce optical loss.
FIG. 3 illustrates the optical fiber block 14 in which a four-core ribbon fiber is to be placed. As shown in FIG. 3, the optical fiber block 14 is divided into an optical-fiber-alignment portion 140 in which a portion of the optical fibers with its coating removed are aligned thereon, and a stress-reduction-depth portion 142 to reduce the stress caused by the coating thickness of the ribbon fiber. A plurality of V grooves 14a is arranged in the optical-fiber-alignment portion 140. The stress-reduction-depth portion 142 is formed with high precision through the wet-etching techniques.
FIG. 4 shows a perspective view of the optical fiber block 14. As shown in FIG. 4, the optical fiber block 14 serves to fix the uncoated portion of the optical fibers BF that are aligned in the V grooves 14a with equal pitches between them. Thus, it is essential to fabricate the V grooves 14a with high precision, and the placement of the glass cover G4 must be accurate. In addition, the alignment of the optical fibers BF must remain fixed using an adhesive B, such as epoxy resin.
However, the conventional optical fiber block generates the following problems in connecting a PLC to an optical fiber. A silicon wafer, from which the conventional optical fiber block is formed, exhibits specific etch characteristics according to the mask design due to its crystalline structure. This makes it impossible to form V-grooves with a 127-μm pitch. As a result, optical fibers may slip from the V grooves. In addition, as the optical fiber block is combined with a glass cover with a large space interposed between them, a large amount of epoxy is unnecessarily used. The extra epoxy may be contracted and expanded during the change in heat, thereby causing misalignment between an optical fiber array and the glass cover. Furthermore, the contraction and expansion of the epoxy is followed by its de-lamination, causing optical loss in the optical fiber component.